This invention relates to a separation process for the recovery of low-boiling hydrocarbons, in which a crude gas containing low-boiling and high-boiling hydrocarbons, is subjected to scrubbing to scrub out the high-boiling components, after which the loaded scrubbing agent is subjected to regeneration and recycled to the scrubbing step.
In the cracking of gas to recover C.sub.2 H.sub.2 (acetylene), there result as by-products, among others, higher acetylenes, i.e., those with more than two carbon atoms in the molecule. In cracked gas produced by partial oxidation, the percentage of higher acetylenes and higher-boiling components in the crude gas mixture is relatively small; however, in cracked gas produced in an electric arc furnace with the exclusion of oxygen, there are appreciable concentrations of higher acetylenes and other high-boilers, such as aromatics. These heavy, high-boiling components are removed by partial condensation and/or by scrubbing out of the cracked gas.
Both chemical and physical scrubbing agents or combinations thereof are used for the scrubbing operation.
For a physical scrubbing step, a polar scrubbing agent is used for scrubbing a series of higher-boiling components from the crude gas mixture. Known scrubbing agents of this type are, for example, methanol, NMP (N-methylpyrrolidone) and DMF (dimethylformamide).
The regeneration of the scrubbing agent loaded with the scrubbed-out components, optionally takes place by stripping with a stripping gas, by lowering the pressure and/or by raising the temperature of the loaded scrubbing agent, so as to drive out the absorbed components. The regenerated scrubbing agent is then recycled to the scrubbing step.
If the scrubbing agent is loaded with temperature-sensitive unsaturated hydrocarbons, which at higher temperatures tend to polymerize or decompose, it is recommended that the regeneration be conducted only by stripping and/or pressure reduction. But such a process, heretofore, had the drawback that if the vapor pressure of the components dissolved in the scrubbing agent were even, in part, below the vapor pressure of the scrubbing agent, the scrubbing agent could be regenerated by stripping only with great difficulty or incompletely.